Motor-driven toothbrush



Aug. 11, 1953 c. B. SMITHSON, JR

MOTOR-DRIVEN TOOTHLBRUSH Filed June 24, 1950 I IN VEN TOR.

6714/9255 5 r/ysa/zu/e.

Mr W

Arrow/52s.

Patented Aug. 11, 1953 UNITED STATE PATENT OFFICE MOTOR-DRIVEN TOOTHBRUSH Charles B. Smithson, Jr., Clay Township, St. Joseph, Ind.

Application June 24, 1950, Serial No; 170,195

.10 Claims. (Cl. 310-47) This inventionreiates to improvements in 1110-tor driven tooth brushes.

The occurrence ofunhealthful conditions of the gum tissues has causeddentists-to conduct extensive investigations into the subject of thecauses and treatment of the condition. Such conditions may-entail eitherswelling of the gums or gingival tissues or recession thereof from theteeth, in each case resulting from cessation of proper functioning ofthe gum tissues. Several treatments have been devised to combat theseconditions. One procedure Which has been eX- tensively tested and whichhas produced favorable results entails a'massaging of the gum tissues.The massaging, if properly performed by oscillations or movements ofsmall amplitude in which the sides of the bristles, rather than the tipsof the bristles of the brush, move in contact with the gum tissues, hasbeen found to stimulate the gum tissues and to overcome the unhealthfulcondition in many instances. The conditions under which the treatment iscarried out areimportant, and one of the important features isthecontrol of the path of the flexing of the brush bristles. An orbitalpath of flexing movement wherein .the dimensions of the path are verysmall, for example, of an amplitude not substantially greaterthanone-eighth of an inch, has been found to be of greatest value. Thepractice fiexure is used in the Charter technique, which technique is arecognized standard for treatment in this field.

The problem of producing the orbital movement uniformly, as treatment iscarried on at both the inner and outer surfaces of the gums andat boththe upper and lower jaws, has been difficult. It will be apparent that,as different sectionsof the mouth are acted upon, the tooth brush mustbe held in different attitudes and at different angles, and theresulthas been difiiculty in maintaining uniformity of the stroke .orpath of the brush bristles as they contact the gum tissues. To secureuniformity and to reduce the amount of time required for the gumtreatment,

it is desirable that means be provided to operate uniformly toaccomplish these results. No such means have been provided heretoforewhich have been fully successful.

One of the conditions encountered with power operated devices has beenthat the treatment requires the exertion of a substantial amount offriction incident to the engagement of multiple brush bristles, with thegum tissue. Even though the brushbristles are pressed lightly againstthe of using ,suchan orbital path of bristlemerals it and gum tissues,the pressure develops a load which use, and which controls accuratelythe desired orbital pathof the brush bristles andwhichmay be used alsofor brushing the teeth.

A further objectof the invention-is toprovide a deviceofthis-characterhaving a casi-ngcon fining a motor and-serving asa.handle for a tooth brush which is drivenbythemotor, wherein thecccentrically operating parts of the device arelocatcd substantiallycentrally with reference to the mass .of the motor and the casing sothat there willnotbe objectional vibration.

A furtherobject of theinvention is to provide a device having. a totally.enclosedcasing which is efiectivelysealedagainst saliva and moistureand which provides for the detachable connectionof a tooth brushtherewith.

Afurther object. is to provide a device of this character .of compactconstruction, wherein novel bearings are provided in the .nature ofelongated tubes rotatably encircling a fixed shaft and providing a largearea of bearing surface.

Afurther object is to provide a novel, detachable, sealed connectionbetween a driving motor and the shank of a brush.

Other objects will be apparent from the following specification.

In the drawing:

Fig. 1 is a top plan view with apart of the casing of'the device removedandwith parts of the device broken away.

Fig. 2 is alongitudinal sectional view taken .on line 2-2 of Fig. 1.

Fig. '3 :is an enlarged longitudinal sectionalview of a modified form ofthe shank portion of a tooth brush.

Fig. 4 isan enlarged transverse sectional view taken on line 4- lof-Fig.2.

.Peeferring toithe drawing which illustrates the preferred embodiment ofthe invention, the nutz designate two registering .parts of a housing orcasing, which parts are adapted to be secured together to form agenerally elongated hollow casing. The casing parts preferably meet at alongitudinal substantially central parting plane and are suitablyribbed, as at M, and apertured at E6 to accommodate securing screws orthe like (not shown) for connecting the housing parts together. Thehousing or casin will preferably be of a character to fit convenientlyand naturally within the palm of the hand, and will preferably be moldedfrom plastic material, hollow rubber, or any other suitable material,preferably of dielectric or non-conductive nature. At one end thehousing parts will be provided with a restricted opening I8 adapted toreceive a grommet or fitting 2|] encircl ng an insulated electrical leadwire or conduit 22 to provide a seal at the end of the casing throughwhich the wire 22 enters the device.

The housing H9, H2 mounts an electric motor which may be of any typefound suitable. A series wound A. C.-D. C. brush type motor ispreferred. This motor has a laminated frame or field lamination unitincluding an end portion 24 encircled by the magnetic coil 26. The motorframe has a plurality of projections by means of which it is secured tothe housing. Thus, as best seen in Fig. 1, the frame may include ears 2Bprojecting from the portion 24 and secured to the rib [4 of the housingpart 52 by means of securing screws 39. A rib or plate extension 32 mayproject from the opposite end portion 34 of the motor frame and besecured by the screw or other securing member 36 to a post-like portion38 formed integrally with the housing l2. At least three points ofconnection of the motor to the frame and the housing are preferred so asto securely anchor the motor.

Plates 49 are anchored to the motor frame or field lamination unit atspaced points to constitute the end bells or end plates thereof. Theplates preferably extend substantially parallel to each other and arespaced outwardly from opposite surfaces of the laminated motor frame.These plates 40 are apertured or socketed to mount the reduced oppositeend portions of a pin or shaft 42. The pin 42 is rotatably encircled byan elongated metal sleeve 44 to which is fixedly secured the laminatedmotor armature 45} positioned to lie within an armature socket of themotor frame and in the plane of the motor frame. The armature 46 isprovided with suitable electric windings 48. The armature 46 is formedin any suitable manner conventional in the art, and has associatedtherewith the commutator portion 50.

The arrangement of the parts is preferably such that the shaft 42 andthe armature will be located in longitudinally spaced relation to thelongitudinal center of the casing l9, l2 so as to leave a spacesubstantially at the center of the housing within the motor frame andbetween the armature 4-6 and the field coil 26. A shaft or pin 52 ispositioned within the last named space, having its opposite ends mountedin sockets in the end plates 49. The shaft 52 will preferably bepositioned exactly parallel to the shaft 42. Felt wicks 56 to retainlubricant are mounted on portions of the pins or shafts 42 and 52 whichproject outwardly from the end plates of the motor. In this connection,each of the two shafts or pins 42 and 52 will preferably be formed ofsintered bronze or any other material characterized by some measure ofporosity, an example of which is well known in the mechanical arts asOilite bearing.

Insulation blocks 59 are carried by the motor frame adjacent to thearmature 46 and each thereof mounts a carrier 69 for a brush E2 whichengages the motor commutator 59. The leads 64 from the electric line 22extend to these brushes, the brushes preferably having a seriesconnection with each other and with the field winding 26. Thisconstruction is well known in the art and provides a compact powerfulmotor which will run freely without danger of overheating.

The sleeve 44 mounts a pinion 66 at one end thereof adjacent to andoutward of the commutator 50. The pinion 66 meshes with a gear or pinion68 which is mounted upon the projecting reduced dimension concentric hubportion If! of an eccentric member or cam 12. The cam 12 is fixed uponan elongated sleeve 14 which rotatably encircles the pin or shaft 52.The cam 12 preferably is of circular peripheral shape or outline, thecenter thereof being eccentric of the center of the sleeve 14 upon whichit is mounted. A ring member 16 encircles the cam ":2, being held inplace by an annular flange or fitting is having a hub portion preferablyfixed upon the sleeve 14. In other words, the ring is is positionedagainst axial displacement by the flange 28 on one end thereof and bythe gear 98 at the opposite end thereof.

The ring 76 mounts a pair of diametrically opposed pins 89 which lie ina direction transverse of the longitudinal dimension of the housing it,l2 and which serve to pivotally connect the fork arms 82 of a rigid yokemember 84 which projects longitudinally forwardly to a point clear ofand spaced longitudinally from the motor frame and field winding 26.This yoke 84 terminates in a laterally bent terminal portion 85.

The end of the housing I0, [2 opposite that mounting the grommet 20 isprovided with an opening or bore 88 of a diameter or size large comparedto the size of the opening l8 at the opposite end of the casing andlarge enough to receive with clearance the terminal end portion of theyoke 84, as best seen in Fig. 1. The bore 88 is interrupted adjacent itsouter end by a circumferential internal groove 92 which receives themarginal portion of a disk 92 which is preferably formed of rubber,synthetic rubber or other flexible material. The member 92 has a centralaperture therein accommodating and having a tight sealing fit around anelongated rigid shank or rod 94 at a point intermediate the length ofthat rod. The rod 94 has a reduced diameter portion 96 at its inner endwhich extends through washers or spacers 98, some of which arepreferably formed of dielectric materia1 and engage opposite surfaces ofthe terminal part 815 of the yoke. The end of rod 94 may bescrew-threaded into a nut 199 to hold said shank in fixedmotion-transmitting relation to the yoke 84. At a point spaced outwardlyfrom the sealing member 92 the rod 94 mounts a cross-pin I92.

The outer surface of the casing is provided with a circumferentialgroove 594 at the end of the casing from which the shaft 94 projects,said groove being spaced from the end of the casing. A sealing member ismounted upon the casing, the same having a skirt portion I99 encirclingthe end of the casing and having an internal bead I98 fitting in thecircumferential groove N34 to anchor the same in place. The bead I08will preferably have a constrictive fit upon the casing to anchor firmlythereto. The skirt HIS-is ofprogressively decreasing size and terminatesin an end portion Iii! having .an aperture providing a constrictivesealing fit around the shaft .94 adjacent to and spaced inwardly fromthe cross-pin N32. The skirt N36 is of such a length that it islongitudinally compressed between its anchorage at points l8i!il8 withthe casing Iii-i2, and its end abutment with the tooth brush mounted onshaft 94, so that it has a circumferential groove or fold H2 therein ata'portion intermediate the end Hil thereof and the end of the casingencircled by the skirt. The fold H2 is important to insure that theaction of the skirt I06 will not act to impose any substantial restraintupon the shaft 94 incident to vibration or oscillation of that shaft.

A tooth brush is provided with a shank portion H 3 having an axial bore1 l6 providing a snug sliding fit upon the shaft 95. The brush shank H4will be provided with a bayonet slot includ ing a socket portion H8adaptedto receive and anchor the cross-pin :22. The constructionillustrated in Fig. 3 is preferred, in which it will be observed that atube or sleeve IZB-serves to line the axial bore ofthe brush shank l4and to have formed therein the bayonet slot H8. The brush head I22 willmount the usual brush bristles PM.

In the operation of the device it will be apparent that as the armatureof the motor is caused to rotate when the motor is energized, it willserve to drive the pinion 66 meshing with the gear 68 fixed upon the hubof the cam 12. The cam 72 will rotate within the ring 16 producing anorbital bodily movement of that ring. The yoke 84, which is pivoted atone end to the ring 16 by the pins transmits the movement of the camring .-'8 to the shank 9-1 and the tooth brush carried thereby. In thisconnection'it will be apparent that the longitudinal component of theorbital movement of the shaft 94 and the brush will be constant at alltimes and will be equal to the eccentricity of the cam. The lateralcomponent of movement of the parts will vary. It will be apparent thatthe member 82 serves as the fulcrum of the oscillatory movement of theshaft 94 and associated parts. Consequently, the extent to which thelateral component of the brush movement occurs will depend uponthe'ratio of the spacing of the brush head from the fulcrum member 92,on the one hand, as compared to the spacing of the yoke pivot 80 fromthe fulcrum member on the other hand. Thus it is possibie by control ofthe ratio of these dimensions to control the orbital path of movementand, where the ratio is not a one-to-one ratio, then the orbitalmovement at the brush bristles will be oval or elliptical. It has beenfound that an orbital movement in which the minor component is .09 inchin extent and the major component is 35 inch is very effective for thepractice of the Charter technique. It will be evident that the parts andthe proportions or ratios can readily be established to provide anorbital movement of such dimensions.

One of the important features of the invention is the journalin of theparts of the motor and the cam. The sleeves 44 and 14, which rotateabout the stationary pins 42 and 52, provide very efiicient bearings. Byreason of the elongated nature of these bearing sleeves, slightclearances of the sleeves upon the pins are not important and thesleeves are effective to hold rotating gears, cams and other parts aboutthe selected 6 axes with minimum tendency toward distortion andwithmaximum bearing surface, allof'which results ,iIL'IBGHCtiOIl ofwear, reduction ofbinding, and insures long life and trouble-freeoperation.

Another feature of the device is that the very nature of the device intranslating rotary motion into oscillatory motion tends toresult in thecreation of vibration. The construction, however, is such that the cam'12 at which the translatory motion occurs is located at thelongitudinal center of the casing. Assuming that the casing is grippednormally :by the finger tips at Or adjacent to the skirt E56 and to thefulcrum of oscillation, with the body of the casing lying in the palm ofthe hand, then the position of cam 12 serves to reduce vibration,because the mass of the motor and the application at 12 of forces equaland opposite to those acting at the fulcrum, tend to absorb thevibration. In other words, the user of the device is not required togrip the device firmly nor to resist the vibration of the device bymanual exertion. At the same time, at the brush head and the brushbristles, the orbital movement or vibration is provided of sufficientlypowerful character so that the desired stimulation of the gum'tissuescan be provided effectively.

The construction of the joint to provide for removable mounting of thetooth brush is of considerable importance. Thus it will be possible thatall members of a family may use the same instrument, without sacrificeof sanitation, by simply providing each member of the family with atooth brush unit so that when any one person desires to use the unit, heapplies his personal tooth brush to the shaft through the detachablecoupling. The pin and bayonet slot connection is particularly wellsuited for this purpose in providing a quick and firm connection. Itwill be apparent, however, that in this construction the skirt 936,being formed of resilient and flexible material and being of a greaterlength than the normal spacing between the butt end of the brush handleor shank and the motor housing, is flexed or folded at I 12. This tendsnormally to apply continuously an outward pressure from the skirt Hi6upon the end member lid to cause it to abut the end surface of the brushshank. The resilience of the parts and the application of pressure bythe skirt against the brush holds the brush at its bayonet slotconnection with the shank and also accommodates the longitudinalcomponent of the oscillatory movement of the shank.

Still another function. of this skirt N36 is to provide a seal so thatsaliva or moisture cannot enter the interior of the motor. This seal isin turn supplemented by the second or inner seal provided by the rubberfulcrum member 92 itself. The important functions of maintenance of apositive saliva seal and the application of pressure to maintain abayonet slot joint connection of parts, all is accomplished in thisconstruction without imposing any substantial loading upon the motor bythose means. In other words, the natural resilience and flexibility ofthe rubber skirt does not tend substantially to damp the lateralcomponents of oscillation of the shaft so that the load upon the motoris maintained at a minimum.

The foregoing features of the construction substantially as describedthus provide a device which satisfies the requirements of usage, adevice which is readily portable and may be carried about whentraveling, a device which is light in weight, compact, strong andreadily usable, a device which is integral in character, and one whichis especially well suited for its intended purpose. Thus by the use ofthe device, each and every part of the gum tissues, both at the innerand outer surfaces of the jaws, may be treated with equal efficacy andwith substantially the same motion. The stimulation of the gums to treatpyorrhea may occur eifectively without substantial effort and withoutthe requirement of any substantial amount of time beyond that requirednormally for tooth brushing purposes.

Whil the preferred embodiment of the invention has been illustrated anddescribed, it will be understood that changes in the construction may bemade within the scope of the appended claims without departing from thespirit of the invention.

I claim:

1. In combination, an electric motor having a housing adapted to be heldin the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally bodily shiftable shaft projecting fromsaid housing, said housing having an aperture receiving said shaft withclearance, a flexible seal spanning said aperture and sealinglyencircling and constrictively gripping said shaft to movably fulcrum thesame intermediate the ends of the shaft, and means for detachablymounting a tooth brush on the projecting portion of said shaft.

In combination, an electric motor having a housing adapted to be held inthe hand, motion translating means actuated by said motor and confinedin said housing, said translating means including an oscillatory andlongitudinally bodily shiftable shaft projecting from said housing, saidhousing having an aperture receiving said shaft with clearance, ayieldable shaft fulcrum mounted in and sealing said aperture, aseparable connector for detachably anchoring a tool shank on theprojecting end of said shaft, and resilient means carried by saidhousing and encircling the projecting portion of said shank to presslongitudinally outwardly against a tool shank at a point spaced from theadjacent end of the housing.

3. In combination, an electric motor having a housing adapted to be heldin the hand, motion translatin means actuated by said motor and confinedin said housing, said translating means including an oscillatory andlongitudinally bodily shiftable shaft projecting from said housing, saidhousing having an aperture receiving said shaft with clearance, ayieldable shaft fulcrum mounted in and sealing said aperture, adetachable connector of the pin and slot type for detachably connectinga tool shank on the projecting part of said shaft, and a resilient sealcarried by and projecting longitudinally from said housing for closingsaid aperture and exerting longitudinal outward pressure on the innerend of said shank to maintain normal interlocking engagement of said pinand slot.

4. In combination, an electric motor having a housing adapted to be heldin the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally bodily shiftable shaft projecting fromsaid housing, said housing having an aperture receiving said shaft withclearance, a yieldable shaft fulcrum mounted in and sealing saidaperture, a detachable connector of the pin and slot type for detachablyconnecting a tool shank on the projecting portion of said shaft spacedfrom said housing, and an elongated resilient skirted member having aconstrictive fit around said housing at a fixed point and a constrictivefit on the projecting portion of said shaft, said skirted member beingadapted to bear against the end of said shank and being of a lengthgreater than the normal spacing between the fixed point of skirtanchorage on said housing and the adjacent end of said shank wherebysaid member is normally compressed longitudinally.

5. In combination, an electric motor having a housing adapted to be heldin the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally shiftable shaft projecting from saidhousing, said housing having an aperture receiving said shaft withclearance, a yielding shaft fulcrum mounted in and sealing saidaperture, and a separable connector for'detachably anchoring a toolshank on the projecting part of said shaft, said housing aperture havinga circumferential groove, said fulcrum constituting a resilient annularmember marginally confined in said groove and constrictively engagingsaid shank.

6. In combination, an electric motor having housing adapted to be heldin the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally bodily shiftable shaft projecting fromsaid housing, said housing having an aperture receiving said shaft withclearance, a separable connector on the projecting part of said shaftfor detachably securing a tool shank on said shaft in spaced relation tosaid housing, and a pair of resilient seals preventing leakage throughsaid aperture around said shaft, one of said seals forming a fulcrum forsaid oscillatory shaft, the other seal projecting longitudinally fromsaid housing and adapted to exert pressure on the inner end of saidshank to maintain said separable connector in operative positionrelative to said shank.

'7. A tool comprising an electric motor having a housing adapted to beheld in the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally shiftable shaft projectin from saidhousing and adapted to detachably mount a tool member, said housinghaving an aperture receiving said shaft with clearance, a yieldablemember carried by said housing and fulcruming said shaft, saidtranslating means including a motor driven cam rotatable on an axistransverse of said shaft and located substantially at the center of massof said motor.

8. A tool comprising an electric motor having a housing adapted to beheld in the hand, motion translating means actuated by said motor andconfined in said housing, said translating means includin an oscillatoryshaft projecting from said housing and adapted to detachably mount atool member, said housing having an aperture receiving said shaft withclearance, a resilient member fuleruming said shaft in said aperture,said translating means including a motor driven cam rotatable on an axistransverse of said shaft and located substantially at the center of massof said motor, a ring slidably encircling said cam, and a yoke embracingand pivoted to said ring, said yoke constituting a rigid extension ofthe inner end of said shaft.

9. A tool comprisin an electric motor having a housing adapted to beheld in the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally shiftable shaft projecting from saidhousing and adapted to detachably mount a tool member, said housinghaving an aperture receiving said shaft with clearance, and a yieldingfulcrum for said shaft mounted in said aperture, said motor including aframe having spaced end plates, a shaft carried by said end plates andextending transversely in said housing, and a sleeve having a snugrotative fit on said shaft and mounting the motor armature.

10. A tool comprising an electric motor having a housing adapted to beheld in the hand, motion translating means actuated by said motor andconfined in said housing, said translating means including anoscillatory and longitudinally shiftable shaft projecting from saidhousing and adapted to detachably mount a tool member, said housinghaving an aperture receiving said shaft with clearance, and a yieldingfulcrum for said shaft mounted in said aperture, said motor including aframe having spaced end plates, a shaft carried by said end plates andextending trans- 10 versely in said housing, and a sleeve having a snugrotative fit on said shaft and mounting the motor armature, said shaftbeing formed of metal characterized by a measure of porosity, andabsorbent members carried by the ends of said shaft outwardly of saidsleeve.

CHARLES B. SMITHSON, JR.

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